In recent years, the treatment of residual and historical wastes from various sources have become a priority for many industries. Due to increasing public awareness and media attention, the exploration, implementation, and importance of cost-effective and environmental friendly approaches for cleaning up sites contaminated with organic contaminants such as petrogenic hydrocarbons has increased significantly, as a mechanism to demonstrate social accountability and environmental sustainability and reduce environmental risk from contaminant exposure and migration, for example.
The environmental remediation industry interested in remediation of contaminated mediums, such as soil and groundwater, have adopted many and various methodologies for treating contaminated soil and/water media. A common practice for remediating soil is either to bury or incinerate (thermal remediation) the contaminated medium (ie. soil or subsurface materials). Burying contaminated media has its obvious disadvantages, mainly that petrogenic contaminants remain mixed with the medium and typically are not removed. Therefore, typically burying contaminated medium only covers up the mess and removes it from visible sight.
Incineration of contaminated soil also has its disadvantages. While combustion of contaminated soil media usually removes substantially all the petrogenic contaminants, it typically also removes all naturally occurring organic carbons such as phytogenic organics as well. In essence, incineration of contaminated medium results in nothing but ash. Further, incineration typically requires input of a large amount of energy. Combustion gases, such as CO2, are typically also released into the atmosphere, which may contribute to global warming and may attract additional costs such as in relation to carbon emissions.
Recently, newer technologies related to thermal remediation of contaminated media have been investigated. For example, microwave heating is a relatively new remediation method, which utilizes electromagnetic (EM) waves to thermally decontaminate contaminated soil or water. A key requirement of microwave remediation is the complete penetration and activation within the treatment medium, whereby the heat created penetrates the interior of the contaminated medium.
U.S. Pat. No. 5,449,889 discloses a system for remediating a medium using a microwave energy source. A portable apparatus for dielectrically heating a medium comprises a microwave energy source having a preselected microwave frequency for emitting microwave energy.
U.S. Pat. No. 5,968,400 discloses a tandem microwave waste disposal system having two combustion chambers used for disposal of waste media, the first one in communication with a source of microwaves, and a second combustion chamber having an input region in communication with a first end of a hollow conduit.
U.S. Pat. No. 4,993,943 introduces an apparatus for the removal of higher and lower volatility organic contaminants from media such as soil. It includes a screw conveyor with an inlet, an outlet and one or more solid core flights. At least one IR source, located on the external side of the screw conveyor, is adapted to heat the media. A continuous process for removing volatility organic contaminants from soil includes agitating, manipulating, and transporting the contaminated media.
Photo-catalytic Purification and Remediation of Contaminated Air and Water, David F. Ollis, 2000 discloses approaches to increase the efficiency of light and catalyst utilization by adding oxidants (hydrogen peroxide), metal ions (silver) and periodic illumination. Hydrogen peroxide enhanced reaction rates by increasing the slow step of trapped electron removal. It diminished electron-hole recombination and increased the selective consumption of holes for surface oxidations. Metal ions increased some rates and catalyzed the electron transfer to molecular oxygen. Periodic illumination provided an increased photo-efficiency by factors up to 5-10 fold.